Par meters are very sensitive to envelope delay distortion.

-frequency characteristic and the envelope delay distortion over a desired frequency range.

Directional dependence of interaural envelope delays.

The specification of the analog channel should include frequency range, bandwidth, signal-to-noise ratio, and envelope delay distortion.

Frequency response (attenuation distortion) and envelope delay distortion are improved by C-conditioning, available in grades C1, C2, or C4.